Laser diffraction measurements of pigment size distributions of coatings and mill bases: implications of dilution medium and dispersion process parameters / Shicong Luo in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 20, N° 3 (05/2023)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 20, N° 3 (05/2023) . - p. 899-917 Titre : Laser diffraction measurements of pigment size distributions of coatings and mill bases: implications of dilution medium and dispersion process parameters Type de document : texte imprimé Auteurs : Shicong Luo, Auteur ; Claus Erik Weinell, Auteur ; Søren Kiil, Auteur Année de publication : 2023 Article en page(s) : p. 899-917 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Broyeurs à billes Dioxyde de titane Dispersions et suspensions Formulation (Génie chimique) Granulométrie laser Microscopie Oxyde de cuivre Pigments Polyacryliques Qualité -- Contrôle Index. décimale : 667.9 Revêtements et enduits Résumé : Coating properties, such as gloss, rheology, and exterior durability, are strongly affected by the particle size distribution (PSD) of pigment agglomerates. Consequently, moving from the industrial practice of a maximum agglomerate size evaluation after dispersion (i.e., grindometer readings) to an accurate measurement of the entire PSD, holds a promising potential for quality control, product optimization, and research. The aim of the present work was to develop an analysis procedure, based on laser diffraction, for PSD measurements of coatings. In the experiments, acrylic-based TiO2 or Cu2O predispersions (i.e., mill bases), with variations in the composition and dispersion parameters, were investigated. Results show that the laser diffraction measurements are influenced by the so-called obscuration value of the diluted sample, the equipment-input refractive index values, and the shape assumption for the pigment agglomerates. Furthermore, the unavoidable sample dilution, prior to a measurement, strongly affects the stability of primary particles and agglomerates. When using a mixture of the pertinent binder and solvent, as opposed to the pure solvent only, and taking rheology issues into consideration, solvent shock was avoided and reliable PSDs could be obtained. The new analytical procedure was used on selected dispersions with variations in coating formulations and equipment operational parameters and allowed for precise detections of the developments in PSDs and volume-moment mean diameters. In summary, the principle of laser diffraction, with proper control of the measurement conditions, was demonstrated to be a reliable technique for PSD evaluation of coatings and predispersions. Note de contenu : - EXPERIMENTAL : Raw materials - Predispersion systems investigated - Dispersion instruments - Laser diffraction particle size analyzer - Scanning electron microscope (SEM) - Digital microscope - Fineness of grind gauge - RESULTS AND DISCUSSION : Pigment size measurements with digital microscopy - Pigment size measurements with electron microscopy - Sensitivity analysis of the user-supplied parameters for the laser diffraction method - Particle shape - Comparison between grind gauge and laser diffraction - PSD measurements of TiO2 - Absence of reagglomeration - Effects on the PSD results of formulation and operational parameters - PSD results of Cu2O obtained using the laser diffraction method - Table 1 : Overview of particle size measuring techniques - Table 2 : Details of pigments used in the experiments - Table 3 : Formulation details of predispersions - Table 4 : Recommended parameters for the laboratory scale high-speed disk disperser - Table 5 : Selected (present investigation) and recommended parameter values for the lab-scale, high-speed bead mill - Table 6 : Details of beads used in the lab-scale, high-speed bead mill - Table 7 : Equivalent spherical diameter of pigment powders, measured using STEM and subsequent image analysis supported by a python code - Table 8 : Volume-moment mean diameter of TiO2-HS1 sample for four obscuration values DOI : https://doi.org/10.1007/s11998-022-00742-7 En ligne : https://link.springer.com/content/pdf/10.1007/s11998-022-00742-7.pdf?pdf=button% [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39436 [article]

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Methanol degradation mechanisms and permeability phenomena in novolac epoxy and polyurethane coatings / Ting Wang in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 18, N° 3 (05/2021)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 18, N° 3 (05/2021) . - p. 831-842 Titre : Methanol degradation mechanisms and permeability phenomena in novolac epoxy and polyurethane coatings Type de document : texte imprimé Auteurs : Ting Wang, Auteur ; Shicong Luo, Auteur ; Chenyu Wang, Auteur ; Jing Wang, Auteur ; Claus Erik Weinell, Auteur ; Kim Dam-Johansen, Auteur ; Juan José Segura, Auteur ; Erik Graversen, Auteur ; Søren Kiil, Auteur Année de publication : 2021 Article en page(s) : p. 831-842 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Absorption Adsorption Epoxy novolac Liaisons hydrogène Méthanol Perméabilité Polyuréthanes Revêtements organiques Index. décimale : 667.9 Revêtements et enduits Résumé : On a global scale, methanol is one of the most important feedstocks and is used widely as solvent and co-solvent. However, due to the polar nature and associated ability to conduct current, the small molecule can take part in galvanic corrosion of metal storage tanks and degrade the barrier properties of protective coatings. In the present work, we investigated the degradation of two novolac epoxy coatings and a polyurethane (PU) coating exposed to methanol with the aim of quantifying the various degradation paths. Absorption and desorption rates were measured and the thermomechanical properties followed by dynamic mechanical analysis. For evaluation of the coating barrier properties (i.e., breakthrough time and steady state permeation rates of methanol), permeation cells were applied. During methanol absorption, simultaneous leaching of certain coating ingredients and bonding of methanol to the binder matrix via hydrogen bonds was evidenced. In terms of classification, the bonding of methanol took place by two types of mechanisms. In Type I, the methanol molecule forms a single hydrogen bond to the coating network, thereby acting as a plasticizer, which decreases the coating storage modulus and glass transition temperature. For Type II bonding of methanol, on the other hand, two hydrogen bonds to the coating network form per molecule, resulting in so-called physical crosslinking. The Type I mechanism boosted segmental mobility and contributed to the leaching of the plasticizer benzyl alcohol from the novolac epoxy coatings and residual solvents (i.e., naphtha and xylene) from the PU coating. Following the methanol desorption, and attributed to an increased effective crosslinking density from Type II bound methanol, the novolac epoxy and PU coatings exhibited significant increases in the glass transition temperatures. In addition, for the three coatings, a gradual decline in the permeability rate of methanol was observed over time. These enhanced (and unexpected) barrier properties result from a combination of effects ascribed to Type II bound methanol and the leaching process. Note de contenu : - Experimental methods for coating degradation studies and aims of the work - EXPERIMENTAL : Materials - Absorption and desorption experiments - Permeation rate experiments - Dynamic mechanical analysis - Gas chromatography-mass spectrometry - RESULTS AND DISCUSSION : Methanol absorption and desorption - Methanol permeation rate - Permeability measurement across thermoplastic films - Permeability measurement across methanol-exposed coating - Water and ethanol absorption and desorption - Table 1 : Main components of the experimental coatings. Additional details can be found in an earlier work on acid degradation of organic coatings. NE-CA = Novolac Epoxy-Cycloaliphatic Amine. NE-PA = Novolac Epoxy-Polyamide - Table 2 : Coating properties and weight changes after immersion for 168 h (Mi) and unrestricted evaporation for 168 h (Ml) of the NE-CA, NE-PA, and PU films - Table 3 : Weight loss (relative to the original nonexposed film), Ml, and the glass transition temperature of the NE-CA, NE-PA, and PU coatings (168 h methanol immersion) - Table 4 : Breakthrough velocity (Rb) and permeation rate (Rperm) of methanol across NE-CA, NE-PA, and PU films - Table 5 : Weight changes of NE-CA films after immersion for 168 h (Mi) followed by unrestricted evaporation for 168 h (Ml) - Scheme : Chemical structures of epoxy phenol novolac resin, copolymer of benzenamine and formaldehyde (one constituent of polyamide), 4,4′-methylenebis(cyclohexylamine) and 1,6-hexamethylene diisocyanate DOI : https://doi.org/10.1007/s11998-020-00446-w En ligne : https://link.springer.com/content/pdf/10.1007/s11998-020-00446-w.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35933 [article]

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On-line, non-Newtonian capillary rheometry for continuous and in-line coatings production / Shicong Luo in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 18, N° 3 (05/2021)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 18, N° 3 (05/2021) . - p. 611-626 Titre : On-line, non-Newtonian capillary rheometry for continuous and in-line coatings production Type de document : texte imprimé Auteurs : Shicong Luo, Auteur ; Claus Erik Weinell, Auteur ; Fridolin Okkels, Auteur ; Anders Landeira Ostergard, Auteur ; Søren Kiil, Auteur Année de publication : 2021 Article en page(s) : p. 611-626 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Fluides non newtoniens Mesure Qualité -- Contrôle Rhéologie Rhéomètres Viscosité Index. décimale : 667.9 Revêtements et enduits Résumé : Moving from traditional batch production into in-line or continuous coatings production requires accurate on-line quality control instruments. The aim of the present work was to investigate the principle of non-Newtonian capillary rheometry for quality control purposes. In the investigation, three series of acrylic-based viscoelastic coating samples with different types and concentrations of pigments and thickening agents were used, and the rheological measurements were compared to results obtained with the so-called Stormer viscometer and an advanced off-line rheometer. A detailed analysis of the potential measurement implications was also conducted. For shear stresses from 15.0 to 350.0 Pa (the upper boundary), the novel capillary rheometer was found to provide results in good quantitative agreement with the advanced rheometer when sample holding time, and thereby shear history, was properly controlled. At a shear stress between 1.0 Pa (lower boundary) and 15.0 Pa, the agreement was not as good, with a difference in results of the non-Newtonian capillary rheometer and the advanced rheometer between 15% and 74%. The resolution of the capillary rheometer was sufficiently high to allow detection of the rheology changes associated with variations in coating formulations of pigment volume and rheology modifier concentrations. In summary, for fast on-line evaluation of coating rheology, the principle of capillarity has been demonstrated to be a varied and robust technique. Note de contenu : - INTRODUCTION - Previous work on on-line and in-line rheometry - Strategy of the investigation - Experimental : Raw materials - Coating systems investigated - Non-Newtonian capillary rheometer - The advanced rheometer - The Sotrmer viscometer - Comparison between different methods - Results and discussion : Evaluation o Reynolds numbers for the non-Newtonian capillary rheometer - Comparison between measurements in the non-Newtonian capillary and the advanced rheometer - Three-interval thixotropy test - Viscosity results when taking into account thixotropic effects of coatings samples - Potential reasons for the lower viscosity results obtained with the non-Newtonian capillary rheometer - Viscosity measurements with the capillary rheometer - Table 1 : Comparison of viscometers (simple) and rheometers (advanced) for in-line and on-line measurements - Table 2 : Compositional details, the critical pigment volume concentration (CPVC), and the reduced PVC (k) of thecoatings used in the investigation - Table 3 : Viscosities measured (at a shear stress of 80 Pa) by the Stormer viscometer, the non-Newtonian capillaryrheometer, and the advanced rheometer - Table 4 : The average viscosity (at two values of shear rate) and the recovery time (i.e., the time required for thesample to reach 90% of the initial viscosity at a shear rate of 0.1 s21) of selected coating samples - Table 5 : Coating viscosities measured with the non-Newtonian capillary rheometer including a 5 min holding time(at a shear stress of 80 Pa) DOI : https://doi.org/10.1007/s11998-020-00447-9 En ligne : https://link.springer.com/content/pdf/10.1007/s11998-020-00447-9.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35916 [article]

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